Refrigerating machine

ABSTRACT

A refrigerating machine having a compressor, a radiator, a pressure-reducing device, a gas-liquid separator, a unit for selectively introducing gas refrigerant separated in the gas-liquid separator into an intermediate pressure portion of the compressor, and a low pressure side circuit in which liquid refrigerant separated in the gas-liquid separator is circulated. The low pressure side circuit is provided with a heat absorbing unit functioning selectively in one of different temperature zones, and refrigerant passing through the selected heat absorbing unit is returned to a suction portion of the compressor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a refrigerating machine having a unitfor selectively introducing gas refrigerant separated in a gas-liquidseparator into an intermediate pressure portion of a compressor.

2. Description of the Related Art

In general, there is known a refrigerating machine having a compressor,a radiator, a pressure-reducing device, a gas-liquid separator and aunit which can introduce gas refrigerant separated in the gas-liquidseparator into an intermediate pressure portion of the compressor asdisclosed in JP-A-2003-106693 (hereinafter referred to as “PatentDocument 1”). In this type of refrigerant machine, gas refrigerantseparated in the gas-liquid separator is introduced into theintermediate pressure portion of the compressor while kept to a gasstate, so that there is achieved an effect that the efficiency of thecompressor can be enhanced.

In some cases, this type of refrigerating machine is equipped with aheat absorbing unit containing heat absorbers which selectively functionin different temperature zone in a refrigerating cycle. For example,when this refrigerating machine is applied to a refrigerator (fridge)having a refrigerating chamber and a freezing chamber, heat absorbersfunctioning as a refrigerator and a freezer are disposed in therefrigerating cycle, and a refrigerating or freezing operation iscarried out by using any one of the heat absorbers. In this case, it isimportant to carry out the refrigerating or freezing operation withoutreducing the efficiency under any operation.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide arefrigerating machine in which when heat absorbing units selectivelyfunctioning in different temperature zones are provided in therefrigerating cycle, the high efficiency operation can be performed inany temperature zone without reducing the efficiency.

In order to attain the above object, according to the present invention,there is provided a refrigerating machine having a compressor, aradiator, a pressure-reducing device, a gas-liquid separator, a unit forselectively introducing gas refrigerant separated in the gas-liquidseparator into an intermediate pressure portion of the compressor, and alow pressure side circuit in which liquid refrigerant separated in thegas-liquid separator is circulated, wherein the low pressure sidecircuit is provided with a heat absorbing unit functioning selectivelyin one of different temperature zones, and refrigerant passing throughthe selected heat absorbing unit is returned to a suction portion of thecompressor.

In this case, it is preferable that the heat absorbing unit has pluralheat absorbers which function in different temperature zones, the heatabsorbers function selectively, and there is provided a unit for guidingcold air passing through the heat absorbers to chambers controlled tothe corresponding temperature zones. Furthermore, the respective heatabsorbers may be disposed in chambers which are respectively controlledto the corresponding temperature zones. Furthermore, the heat absorbingunit may be provided with one heat absorber which functions selectivelyin different temperature zones, and there is provided a unit forselectively guiding cold air passing through the heat absorber through achange-over dumper to plural chambers controlled to differenttemperature zones. In this case, the heat absorber may be disposed in achamber controlled to a low temperature zone.

Furthermore, in all the cases described above, refrigerant such ascarbon dioxide refrigerant or the like with which the high pressure sideis set to supercritical pressure under operation may be filled.

According to the present invention, the low pressure side circuit forcirculating liquid refrigerant separated in the gas-liquid separator isprovided, and the low pressure side circuit is provided with theabsorbing unit which selectively functions in different temperaturezones. Therefore, high-efficiency operation can be performed in therespective temperature zones.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a refrigerant circuit diagram showing an embodiment of arefrigerating machine according to the present invention;

FIG. 2 is an enthalpy-pressure diagram of a refrigerating cycle;

FIG. 3 is an enthalpy-pressure diagram of a supercritical cycle;

FIG. 4 is a diagram showing an applied example to a refrigerator;

FIG. 5 is a diagram showing a cooling example;

FIG. 6 is a diagram showing a cooling example;

FIG. 7 is a diagram showing an applied example to a refrigerator;

FIG. 8 is a diagram showing an applied example to a refrigerator;

FIG. 9 is a refrigerant circuit diagram showing another embodiment;

FIG. 10 is a diagram showing an applied example to a refrigerator; and

FIG. 11 is a diagram showing an applied example to a refrigerator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments according to the present invention will bedescribed hereunder with reference to the accompanying drawings.

FIG. 1 is a refrigerant circuit diagram showing an embodiment of thepresent invention.

A refrigerating machine 30 has a compressor 1, a radiator 2, apressure-reducing device 3 and a gas-liquid separator 4. A refrigerantcircuit extending from the compressor 1 through the radiator 2 to theinlet port of the pressure-reducing device 3 constitutes a high pressureside circuit. The pressure-reducing device 3 is designed so that theopening degree of the diaphragm thereof is variable. By varying theopening degree, the pressure of refrigerant is reduced until therefrigerant reaches the gas-liquid separator 4, and a lot of gasrefrigerant occurs. Under this state, the refrigerant is input to thegas-liquid separator 4, whereby the separation efficiency in thegas-liquid separator 4 can be varied. The compressor 1 is a two-stagecompressor, and it contains a first-stage compressing portion 1A, asecond-stage compressing portion 1B and an intermediate cooler 1Cbetween the first-stage compressing portion 1A and the second-stagecompressing portion 1B. Reference numeral 8 represents a check valve.

The refrigerating machine 30 has an introducing unit which can introducegas refrigerant separated in the gas-liquid separator 4 to theintermediate portion of the compressor 1, that is, between theintermediate cooler 1C and the second-stage compressing portion 1B. Thecompressor is not limited to the two-stage compressor. For example, whenthe compressor is a one-stage compressor, the introducing unit 5 mayreturn the refrigerant to the intermediate pressure portion of theone-stage compressor. The introducing unit 5 comprises a gas pipe 6 andan opening/closing valve 7 provided to the gas pipe 6. When theopening/closing valve 7 is opened, the gas refrigerant separated in thegas-liquid separator 4 is passed through the gas pipe 6, and introducedto the intermediate pressure portion of the compressor 1 as indicated byan arrow of a broken line due to the pressure difference in the gas pipe6.

Furthermore, the refrigerating machine 30 is provided with a lowpressure side circuit 9 for circulating liquid refrigerant separated inthe gas-liquid separator 4, and the low pressure side circuit 9 isprovided with a heat absorbing unit 10 which functions selectively indifferent temperature zones. The heat absorbing unit 10 comprises athree-way valve 11, a first capillary tube 12, a second capillary tube13 provided in parallel to the first capillary tube 12, and one heatabsorber 14.

The resistance value of the first capillary tube 12 is set to be largerthan the resistance value of the second capillary tube 13. Therefore,when the refrigerant is made to flow to the first capillary tube 12 byswitching the three-way valve 11 and also the driving frequency of thecompressor 1 is reduced, the flow amount of the refrigerant flowing intothe heat absorber 14 is reduced, the evaporation temperature isincreased and thus refrigerating operation is carried out. When thedriving frequency is fixed and only the resistance value of thecapillary tube is increased, the evaporation temperature is lowered.Furthermore, when the refrigerant is made to flow to the secondcapillary tube 13 and the driving frequency of the compressor 1 isincreased, the flow amount of the refrigerant flowing into the heatabsorber 14 is increased, the evaporation temperature is lowered and thefreezing operation is carried out. The refrigerant passed through theheat absorber 14 is passed through a heat exchanger 15 disposed near tothe pressure-reducing device 3, heat-exchanged by the heat exchanger 15to be heated. The refrigerant thus heated is passed through a checkvalve 8, and then returned to the suction portion of the compressor 1.

The above construction is equipped with a unit 23 for selectivelyguiding cold air passed through the heat absorber 14 to plural chambers(refrigerating chamber 21, freezing chamber 22) controlled to differenttemperature zones. The unit 23 contains an air blowing duct 24 and achange-over dumper 25. A controller 26 is connected to the change-overdumper 25. The controller 26 is connected to the three-way valve 11. Forexample when the load of the freezing chamber 22 is increased, byswitching the three valve 11, the refrigerant is made to successivelyflow through the second capillary tube 13 having the small resistancevalue and the heat absorbing unit in this order. The evaporationtemperature in the heat absorber 14 is reduced, and the change-overdumper 25 is tilted to the position shown in FIG. 1 to guide cold air tothe freezing chamber 22. When the load of the refrigerating chamber 21is increased, by switching the three-way valve 11, the refrigerant ismade to successively flow through the first capillary tube 12 having alarge resistance value and the heat absorber 14 in this order, and theevaporator temperature in the heat absorber 14 is increased. Then, thechange-over dumper 25 is titled to the opposite side to the positionshown in FIG. 1 to guide cold air to the refrigerating chamber 21.

The refrigerant with which the high pressure side is set tosupercritical pressure during operation, for example, carbon dioxiderefrigerant is filled in the refrigerant circuit described above.

FIG. 2 is an enthalpy-pressure (ph) diagram of the refrigerating cyclecontaining the two-stage compressor of this embodiment. In thisembodiment, under such a condition that the outside air temperature isincreased to 30° or more in summer or the load is increased, the highpressure side circuit is driven at supercritical pressure duringoperation as indicated by the enthalpy-pressure (ph) diagram of FIG. 3.The refrigerant with which the high-pressure circuit is driven atsupercritical pressure may contain ethylene, diborane, ethane, nitrideoxide or the like.

Next, the refrigerating cycle of the two-stage compressor 1 will bedescribed with reference to FIGS. 2 and 3.

In FIGS. 2 and 3, “a” represents a ph value at the suction port of thefirst-stage compressing portion 1A, “b” represents a ph value at thedischarge port of the first-stage compressing portion 1A, “c” representsa ph value at the outlet port of the intermediate cooler 1C, “d”represents a ph value at the suction port of the second-stagecompressing portion 1B, and “e” represents the discharge port of thesecond-stage compressing portion 1A. The refrigerant discharge from thecompressor 1 is passed through the radiator 2 and circulated and cooled.“f” represents a ph value at the outlet port of the radiator 2, “g”represents a ph value at the inlet port of the pressure-reducing device3, and “h” represents a ph value at the outlet port of thepressure-reducing device 3. Under this state, the refrigerant becomes atwo-phase mixture of gas/liquid. The ratio of gas and liquid correspondsto the ratio of the length of a line segment (gas) h-i and the length ofa line segment (liquid) h-n. The refrigerant enters the gas-liquidseparator 4 under the two-phase mixture. The gas refrigerant separatedin the gas-liquid separator 4 is introduced to the intermediate pressureportion of the compressor 1, that is, introduced between theintermediate cooler 1C and the second-stage compressing portion 1B. “n”represents a ph value at the outlet port of the gas-liquid separator 4.The refrigerant passed through the outlet port of the gas-liquidseparator 4 reaches the suction port of the second-stage compressingportion 1B of “d”, and is compressed in the second-stage compressingportion 1A. On the other hand, the liquid refrigerant separated in thegas-liquid separator 4 is circulated in the low pressure side circuit 9.“i” represents a ph value at the outlet port of the gas-liquid separator4, “i” represents a ph value at the inlet port of one of the firstcapillary tube 12 and the second capillary tube 13, “k” represents a phvalue at the outlet port of one of the first and second capillary tubes12 and 13, and “1” represents a ph value at the outlet port of the heatabsorber 14. The refrigerant of gas phase is passed through the checkvalve 8 and returned to the suction port of the first-stage compressingportion 1A of “a”.

In the above construction, the gas refrigerant separated in thegas-liquid separator 4 is not usable for cooling even when it iscirculated to the low pressure side circuit 9, and returning of this gasrefrigerant to the suction port of the first-stage compressing portion1A reduces the compression efficiency of the compressor 1.

In this construction, the gas refrigerant separated in the gas-liquidseparator 4 is introduced to the intermediate pressure portion of thecompressor 1, that is, between the intermediate cooler 1C and thesecond-stage compressing portion 1B, and thus the compression efficiencyof the compressor 1 can be enhanced. In this embodiment, particularlycarbon dioxide refrigerant is filled in the refrigerant circuit, andthus with respect to the ratio of gas and liquid which are separatedfrom each other in the gas-liquid separator 4, the gas amount (the linesegment h-i) is larger as compared with chlorofluorocarbon refrigerant,and the large amount of gas refrigerant is introduced to theintermediate pressure portion of the compressor 1 to thereby enhance theefficiency.

In this embodiment, all the constituent elements of the heat absorbingunit 10 functioning selectively in different temperature zones, that is,the three-way valve 11, the first and second capillary tubes 12 and 13and the heat absorber 14 are provided in the low pressure side circuit 9in which the liquid refrigerant separated in the gas-liquid separator 4is circulated. Therefore, for example in both the cases whererefrigerating operation is carried out and where freezing operation iscarried out, the high-efficiency operation can be performed withoutreducing the efficiency.

FIG. 4 shows an example in which the above embodiment is applied to arefrigerator.

A refrigerator 40 has a refrigerating chamber 41 at the upper stage, anda freezing chamber 42 at a lower stage. A refrigerator partition wall 43is provided at an inner back side of the freezing chamber 42, and theheat absorber 14 is disposed in an air flow path 44 partitioned by therefrigerator partition wall 43. A first change-over dumper 45 isdisposed at the inlet port of the air flow path 44, and the firstchange-over duper 45 is switched between a closing position (broken-lineposition) at which the inlet port A of the air flow path 44 is closedand an opening position (solid-line position) at which the inlet port Aof the air flow path 44 is opened. Furthermore, a back-side air flowpath 46 is formed in the back wall 47 of the refrigerator 40, and whenthe first change-over dumper 45 is switched to the broken-line position,the inlet port A of the air flow path 44 and the refrigerating chamber41 intercommunicate with each other through the back-side air flow path46. A fan 48 and a second change-over dumper 49 are disposed at theoutlet port B of the air flow path 44, and the second change-over dumper49 is switched between a closing position (broken-line position) atwhich the outlet port B of the air blow path 44 is closed and an openingposition (solid-line position) at which the outlet port B of the airblow path 44 is opened. At the solid-line position, the secondchange-over dumper 49 closes an opening 51 of an intermediate partitionwall 50.

FIG. 5 shows an cooling example 1.

The area from the initial point to the point a corresponds to thefreezing operation. Referring to FIG. 4 (the dumpers 45 and 49 arelocated at the solid-line positions), cold air cooled by the heatabsorber 14 is circulated in the air flow path 44, and fed to thefreezing chamber 42, whereby the temperature of the freezing chamber 42is gradually reduced. On the other hand, the temperature of therefrigerating chamber 41 to which no cold air is fed is graduallyincreased. During this period, the compressor 1 is turned on, the fan 48is turned on, and each of the dumpers 45 and 49 is switched to thesolid-line position. By switching the three-way valve 11, refrigerant ismade to flow into the second capillary tube 13, and the opening/closingvalve 7 is opened. From a point to b point, the operation is stopped.During this period, no cold air is fed to both the refrigerating chamber41 and the freezing chamber 42, and the temperature of each of thechambers 41 and 42 is gradually increased. That is, the compressor 1 isturned off and the fan 48 is turned off. In addition, each of thedumpers 45 and 49 is kept to the solid-line position and the three-wayvalve 11 is fully closed while the opening/closing valve 7 is closed.From b point to c point, the refrigerating operation is carried out.Referring to FIG. 4 (the dumpers 45 and 49 are set to the broken-linepositions), air in the refrigerating chamber 41 is circulated throughthe back-side air flow path 46, and cold air cooled by the heat absorber14 is fed through the opening 51 of the intermediate partition wall 50to the refrigerating chamber 41. Accordingly, the temperature of therefrigerating chamber 41 turns into reduction, however, the temperatureof the freezing chamber 42 to which no cold air is fed keeps increase.During this period, the compressor 1 is turned on, the fan 48 is turnedon, each of the dumpers 45 and 49 is switched to the broken-lineposition, and the three-way valve 11 is switched, so that therefrigerant flows into the first capillary tube 12. When therefrigerating operation is started, the opening/closing valve 7 isopened with a predetermined time delay in order to prevent short-cut ofthe refrigerant passing through the opening/closing valve 7 at the starttime of the operation of the compressor 1. Subsequently, this control isrepeated from d point to i point.

FIG. 6 shows a cooling example 2.

The time period from 1 point to m point corresponds to the freezingoperation. Referring to FIG. 4 (the dumpers 45 and 49 are set to thesolid-line position), and cold air cooled by the heat absorber 14 iscirculated in the air flow path 44 and fed to the freezing chamber 42.Accordingly, the temperature of the freezing chamber 42 is graduallyreduced. On the other hand, the temperature of the refrigerating chamber41 to which no cold air is fed is gradually increased. During this timeperiod, the compressor 1 is turned on, the fan 48 is turned on, each ofthe dumpers 45 and 49 is switched to the solid-line position and thethree-way valve 11 is switched, so that the refrigerant is made to flowin the second capillary tube 13 and the opening/closing valve 7 isopened. From the time period from m point to n point, the refrigeratingoperation is carried out. Referring to FIG. 4 (the dumpers 45 and 49 areset to the broken-line positions), air in the refrigerating chamber 41is circulated through the back-side air blow path 46, and cold aircooled by the heat absorber 14 is passed through the opening 51 of theintermediate partition wall 50 to the refrigerating chamber 41.Accordingly, the temperature of the refrigerating chamber 41 turns intoreduction, however, the temperature of the freezing chamber 42 to whichno cold air is fed turns into increase. During this period, thecompressor 1 and the fan 48 are kept to ON-state, each of the dumpers 45and 49 is switched to the broken-line position, and the three-way valve11 is switched, so that the refrigerant is made to flow into the firstcapillary tube 12. From the time period from n point too point, theoperation is stopped. During this period, no cold air is fed to both therefrigerating chamber 41 and the freezing chamber 42, and thetemperature of each of the chambers 41 and 42 is gradually increased.That is, the compressor 1 is turned off and the fan 48 is turned off.Both the dumpers 45 and 49 are not switched, and kept to the broken-linepositions. The three-way valve 11 is fully closed, and the opening valve7 is closed. Subsequently, this control is repeated during the timeperiod from p point to s point.

FIG. 7 shows another embodiment. This embodiment is different from theembodiment shown in FIG. 4 in the dumper construction at the outlet andinlet ports of the air flow path 44. The dumper at the inlet port A isconstructed by two dumpers 145A and 145B, and the dumper at the outletport B is constructed by two dumpers 149A and 149B.

FIG. 8 shows another embodiment. This embodiment is different from theembodiment of FIG. 4 in the construction of the heat absorbing unit 10.That is, the heat absorbing unit 10 comprises a fourth capillary tube 55and an electric motor operated valve 56 connected t the fourth capillarytube 55 in series. Reference numeral 54 represents an electric motoroperated valve. The fourth capillary tube 55 has a fixed resistancevalue, and the overall resistance value can be varied by adjusting theresistance value of the fourth capillary tube 55 and the valve openingdegree of the electric motor operated valve 56, so that therefrigeration or freezing operation can be performed. Substantially thesame effect as the above embodiment can be achieved.

FIG. 9 shows the construction of another refrigerant circuit.

This construction is different from the construction shown in FIG. 1 inthe construction of the heat absorbing unit 10. The heating unit of thisembodiment comprises a three-way valve 11, a first capillary tube 12, aheat absorber for refrigeration which is connected to the firstcapillary tube 12 in series, a second capillary tube 13 which isprovided in parallel to the above elements, and a heat absorber 58 forfreezing which is connected to the second capillary tube 13. Referencenumeral 59 represents a check valve.

FIG. 10 shows an applied example to a refrigerator. The refrigerator 40has a refrigerating chamber 41 at the upper stage and a freezing chamber42 at the lower stage. Inner partition walls 61 and 62 are provided atthe inner back sides of the respective chambers 41 and 42, and the heatabsorbers 57 and 58 and fans 63 and 64 are provided in the air flowpaths 44 partitioned by the inner partition walls 61 and 62,respectively. In this construction, the three-way valve 11 is switchedin accordance with the thermo-on, thermo-off of the refrigeratingoperation and the freezing operation so that refrigerant is made to flowinto any one of the heat absorbers 57 and 58, and the corresponding fan62 or 63 is operated.

FIG. 11 shows another construction.

This construction is different from the construction of FIG. 10 in theconstruction of the heat absorbing unit 10. The three-way valve iseliminated from the heat absorbing unit 10, however, electric motoroperated valves 65 and 66 are connected to the capillary tubes 12 and13, respectively. Reference numeral 67 represents an electric motoroperated valve. In this construction, the electric motor operated valves65 and 66 are turned on or off in accordance with the thermo-on orthermo-off of the refrigerating operation and the freezing operation sothat refrigerant is made to selectively flow into any one of the heatabsorbers 57 and d58, and also the corresponding fan 62 or 63 is driven.In these embodiments, the same effect as the embodiment described abovecan be achieved.

The present invention is not limited to the above embodiments, andvarious modifications may be made without departing from the subjectmatter of the present invention. In the above embodiments, carbondioxide refrigerant is filled in the refrigerant circuit, however, therefrigerant used in the present invention is not limited to carbondioxide. For example, chlorofluorocarbon (Freon) type refrigerant or thelike may be used.

1. A refrigerating machine comprising a compressor, a radiator, apressure-reducing device, a gas-liquid separator, a unit for selectivelyintroducing gas refrigerant separated in the gas-liquid separator intoan intermediate pressure portion of the compressor, and a low pressureside circuit in which liquid refrigerant separated in the gas-liquidseparator is circulated, wherein the low pressure side circuit isprovided with a heat absorbing unit functioning selectively in one ofdifferent temperature zones, and refrigerant passing through theselected heat absorbing unit is returned to a suction portion of thecompressor.
 2. The refrigerating machine according to claim 1, whereinthe heat absorbing unit has plural heat absorbers functioning indifferent temperature zones, the heat absorbers selectively function,and the refrigerating machine further comprises a unit for guiding coldair passing through the heat absorbers to chambers controlled to thecorresponding temperature zones.
 3. The refrigerating machine accordingto claim 2, wherein the respective heat absorbers are disposed in thechambers controlled to the corresponding temperature zones.
 4. Therefrigerating machine according to claim 1, wherein the heat absorbingunit is provided with one heat absorber which functions selectively indifferent temperature zones, and the refrigerating machine furthercomprises a unit for selectively guiding cold air passing through theheat absorber through a change-over dumper to plural chambers controlledto different temperature zones.
 5. The refrigerating machine accordingto claim 4, wherein the heat absorber is disposed in a chambercontrolled to a low temperature zone.
 6. The refrigerating machineaccording to claim 1, wherein the refrigerant is formed of refrigerantwith which the high pressure side is set to supercritical pressure underoperation.
 7. The refrigerating machine according to claim 6, whereinthe refrigerant is formed of carbon dioxide.